The present invention relates generally to apparatus for controlling the transmission of rotational forces between first and second relatively rotatable members. More particularly, the invention is directed to the arrangement of a forced air cooling system and a power transfer coupling incorporated in a rotational control apparatus in order to increase the useful life and minimize required service operations for the apparatus.
It is often desired to selectively interconnect a rotatable power transmission member with an output element in order to either couple the output element with the power transmission member for concurrent rotation or to brake the power transmission member. For instance, when it is desired to intermittently transmit rotational forces from a power transmission member to a relatively rotatably output element, it is commonplace to interconnect the components with a clutch and then to selectively activate and deactivate the clutch as needed. Known clutch arrangements can be controlled utilizing electrical, mechanical, pneumatic or hydraulic based actuation systems which typically function to axially shift a friction disc, that is mounted for concurrent rotation with the power transfer member, into engagement with the output element.
When the friction disc engages the output element, a significant amount of thermal energy is developed at the friction interface. The rate at which this thermal energy can be dissipated directly affects the permissible cycling times for the apparatus. For this reason, it is also known in the art to provide a flow of cooling air to the friction interface to increase the thermal dissipation capacity of the friction disc in order to allow for greater cycling times. of course, the various components of the rotational control apparatus must be mounted through suitable bearings to enable relative rotation therebetween. Although it is desired to design the apparatus so as to be as compact as possible in order to minimize material and assembly costs, care must be taken in the design of such apparatus to avoid exposing the bearings to excessive heat factors, which can result in grease breakdown, and unnecessary loading, which can cause premature bearing failure.
Based on the above problems, clutch and brake manufacturers are often forced to size rotational control apparatus larger than desired and to specifically configure the components to avoid undue loading and heat exposure of the bearings. Therefore, there exists a need in the art for a rotational control apparatus which is extremely compact, but yet which is designed to ensure an enhanced useful life.